Duffy Gaver has built some bad@ss celebrity bodies, including those of Brad Pitt and Channing Tatum. Only you’d never hear it from him. Despite being one of Hollywood’s elite trainers, Duffy attacks his job with a humble, down-to-earth, hard-as-nails, move-your-butts attitude.

He doesn’t drop names; he makes you drop and give him 20. Followed by 20 more. And 20 more after that. And… you get the picture. In Duffy’s eyes, “All fitness is good fitness.”

Scarlett Johansson and Chris Hemsworth just graduated from the School of Duffy with degrees in crushing faces, pulverizing villains, and avenging the planet. The ex-Navy SEAL spent time with Bodybuilding.com to show us how he helped Hemsworth put on 25 pounds of Thor-muscle and turned Johansson into a lean, mean, bad-guy-busting machine.

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